Improvement in blackboards



J. W. 0 GILMAN.

BLACKBOARD.

No. 182,065; Patented Sept. 12,1876.

NJETERS, PNOTO-LITHOLIHAPhER. WASHINGTON. D. C.

UNITED STATES PATENT Qrrrcn JONATHAN O. GILMAN, OF MALDEN,MASSACHUSETTS.

IMPROVEMENT m BLACKBOARDS.

Specification forming part of Letters Patent No. 182,065, datedSeptember 12, 1876 application filed June 29, 1876.

To all whom it may concern:

Be it known that I, J ONATHANW. O. GIL- MAN, of Malden, in the county ofMiddlesex and State of Massachusetts, have invented an Improvement inInstructors Blackboards, of which the following is a specification:

In teaching drawing, writing, map-making,

. surveying, platting, and like branches where the pupil is to be taughtin any respect graphic construction, or is to use. graphic illustration,it has been observed that the pupils make more rapid advances if theinstructor accompanies and illustrates on the blackboard. to the pupil,explaining as he goes along the example which the pupils are doing attheir respective desks; but it frequently happens that the teacher isdeficient in the manual dexterity for this work, and is reluctant toattempt it, and the pupils are either obliged to be content either withthe text-book alone or with an oral explanation more or less borrowedfrom the text-book without the graphic demonstration.

This invention is intended to furnish to the instructor a means ofillustrating common branches accurately, and yet without demanding theskill in .which they are deficient. It

consists in printing, in low tone, on the prepared surfaces ofpasteboard, so generally in, use as slates, writing and drawing tablets,and blaekboards,'the guide-lines and constructionlines, and theillustration itself, in so low a .tone that, though distinguishable tothe demonstrator at the board, it is indistinguishable to the pupils attheir distance.

A variety of designs may be printed over each other,'the lines of eachdiagram being uniform in tint but distinguished into construction-linesof form by being slotted or continuous, and the diagrams having each atint of its own; but I prefer, in lieu of this, 'to print only onediagram to a board and to make it by covering the board, except on thediagram-lines, with the tint, and leaving the gritty blackboard-surfaceto take the chalk.

. The instructor goes over with chalk the lines of the diagrams he 1sinstructing upon, dotting the dotted lines, making the continuous linescontinuous, and shading the shaded lines, explaining as he goes. Thescholars thus see every part growing before their eyes equally withtheir own advance with the copies under their hands.

To illustrate by drawing, so far as may be, this invention, I have takena set of capitals of the modern type. I have made constructon-lines toillustrate their formation, as follows: The base-line and head-line,measuring the vertical extension of the letters, are dotted inhorizontally, and another horizontal dotted line is drawn half-waybetween them to form the boundary upward for the tails of such lettersas A, E, F, G, H, I, K, M, N, S, T. Other horizontal lines are dotted inabove and belowthis median line, substantially or in a difl'erentdotting, so as to divide the space between the base and head lines intothirds, and serve as boundaries to parts of the T, F, H, K, Y, W, D, A,R, and so on. Slope-lines indicating the slope of the letters are alsodotted in. These straight lines form the ordinates and abscissas, as itwere, of the curves we are about to construct.

In the drawing, the base-line is numbered 1, the headline 2, the medianline 3, the upper thirds-line 4, the lower thirds-line 5, and theslope-line 6. The teacher brings this all out on the board in chalk,marking over the lines printed in low tone, and imperceptible to thepupil, explaining as he goes. Having now got to the point of forming theletters, the instructor goes on explaining that, in capital script, theletters are each and all soreferable to ovals inscribed on theslope-lines as a long v diameter, and touching each other, that it willbe found of great assistance to learn to make such accurately, and heproceeds to draw in a series of ovals, also as construction-lines,forming frequently parts of letters. Then taking the letters one by one,he draws and shades them, pointing out and explaining as he goes ,theirrelations to the construction lines and ovals. It will be readily seenthat, by having these things all on the boards in low tone to be coveredby chalk, the work of the teacher is much facilitated. It is necessary,in closing this work, to select forthe tints colors of very little body,and to mix them so as not to polish the surface or render it greasy.Transparent white ink is perhaps the best, and inks made with aimi imumnof oil are. better, than.ordi-' nary printers ink.

The described improvement in instructors blackboards, consisting of ablackboard-surface, prepared for Writing or drawing with ehaik,'andhaving;faintly printed thereon, in

tints of low tone, construction-lines, illustrai- 7 tions, .ancidiagrams' to besuccessiveiydeveloped andbroug htout by the teacher by theaid of chalk-drawing, substantially as and for the purpose described.

JONATHAN W. O. GILMAN.

Witnesses;

T-HOS. WM. CLARKE, FREE. F. RAYMOND.

